1. Field of the Invention
The invention relates to a method for the treatment of mineral fillers using organic phosphate treatment agents.
The invention also relates to the mineral fillers so treated and that can be suspended in a polyol.
The invention also relates to such suspensions of these treated mineral fillers in polyols, as well as to their use in the manufacture of flexible, semirigid, or rigid polyurethane foams.
Finally, the invention relates to the use of flexible, semirigid, or rigid polyurethane foams containing these treated mineral fillers in the manufacture of molded or nonmolded objects.
2. Description of the Prior Art
To decrease the cost price per liter and per kilogram of molded or nonmolded objects made from flexible, semirigid, or rigid polyurethane foams, it has been increasingly necessary to increase the quantity of filler present in the flexible, semirigid, or rigid polyurethane foams while at the same time preserving or improving their physicochemical properties, such as, compression, or their aesthetic or other properties, such as fire retardation, which are desired in various fields of industry such as, notably, transports (for example, cars and furniture) and in construction or other fields.
Several methods exist today to introduce mineral fillers, such as calcium carbonate, into these polyurethane compounds.
In a first type of method (French Patent No. 2,651,238), calcium carbonate is introduced into a plasticizer for polyurethane. However, this method for obtaining a suspension of a filler in a plasticizer, which permits increasing the content of the filler in the polyurethane compound, is not suitable for the following reasons. Its cost is high and its use is excessively difficult in the manufacture of flexible, semirigid, or rigid polyurethane foams. In addition, the physicochemical properties of the foams obtained from such suspensions are degraded.
Applicants have invented a method which completely favors the introduction of mineral fillers into flexible, semirigid, or rigid polyurethane foams using an inexpensive, simple means that does not result in any problems involving a significant decrease in the reactivity of the polyurethane foams.
Applicants"" method is an improvement over other methods for the introduction of the filler into the polyol, one of the constituents of the polyurethane, that are known to a person skilled in the art.
A first type of method discloses grafting of methacrylic acid (German Patent Nos. 2,654,746, 2,714,291, and 2,739,620) or of another vinyl compound such as styrene on the polyol. However, this type of method does not allow the use of a suspension of calcium carbonate in the polyol because the suspension is too difficult to handle as a result of an excessively high viscosity and a poor distribution of the filler in the medium.
Another type of method involves treating the filler at the surface prior to its introduction into the polyol by means of an agent that is, for example, an alcohol with 8-14 carbon atoms (French Patent No. 2,531,971) or a hydroxycarboxylic acid phosphate (European Patent No. 0,202,394).
However, these methods produce the same type of drawbacks as those cited above since the user is confronted with problems of poor dispersibilityxe2x80x94in the polyolxe2x80x94of the mineral filler so treated.
Thus, the techniques heretofore known do not solve the problem of suspending mineral fillers in the polyol, which mineral fillers are intended to be used in the manufacture of flexible, semirigid, or rigid polyurethane foams.
In order to solve this problem, the applicant developed a method for the treatment of a mineral filler by means of at least one organic phosphate treatment agent, as well as a mineral filler so treated that allows, in an unexpected manner, for the production of a suspension of a mineral filler in polyols with a high content of the filler and a low viscosity; that is, a homogeneous suspension not subject to serious sedimentation, decanting, or thickening in the manufacture of flexible, semirigid, or rigid polyurethane foams.
Thus, one of the objectives of the invention is the development of a method for the treatment of mineral fillers for use in a suspension in polyols, using at least one treatment agent of the organic phosphate type with the general formula (I): 
with R1=H, C8-C40 alkyl, or C6-C40 aryl, alkylaryl, or arylalkyl radical,
with R2=C8-C40 alkyl or C6-C40 aryl, alkylaryl, or arylalkyl radical 
(m+n) varies from 0 to 30 with mxe2x89xa630 and nxe2x89xa630
(p+q) varies from 0 to 30 with pxe2x89xa630 and qxe2x89xa630
Another objective of the invention is the development of these treated mineral fillers which exhibit an uptake of polyol which is decreased by at least 15%, preferably at least 20%, with respect to uptake of polyol using the untreated mineral filler, while at the same time preserving the hydrophilicity of the untreated mineral fillers.
Another objective of the invention is the development of homogeneous, stable, and low-viscosity suspensions of these treated mineral fillers in the polyols, characterized by a concentration by weight of mineral fillers that can be up to 80% and a treatment agent content up to 0.5-3 wt % based on the dry weight of the filler.
These homogeneous, stable, and low-viscosity suspensions according to the invention can easily be handled because, under normal conditions of use, they present no decanting phenomenon, that is, no separation into two phases; no sedimentation, that is, no presence of a hard deposit at the bottom of the vessel in which the suspension is stored; and no serious thickening, thus allowing for the production of flexible, semirigid, or rigid polyurethane foams with excellent physicochemical properties.
Finally, another objective of the invention is the use of these homogeneous, stable, and low-viscosity suspensions of mineral fillers in the manufacture of flexible, semirigid, or rigid polyurethane foams as well as the use of said foams in the manufacture of molded or nonmolded objects.
These objectives are attained by a preferred treatment method according to which at least one treatment agent with the general formula (I) is mixed with the mineral filler to be treated so as to obtain a homogeneity factor (HF) of less than 0.2, preferably less than 0.10, and very preferably less than 0.05, with said factor being defined as the difference in weight between the retained material during dry sieving of the treated fillers and the retained material during dry sieving of nontreated fillers, which is expressed by the formula:   HF  =                                                        (                              weight                ⁢                                  xe2x80x83                                ⁢                of                ⁢                                  xe2x80x83                                ⁢                the                ⁢                                  xe2x80x83                                ⁢                treated                ⁢                                  xe2x80x83                                ⁢                filler                                                                                                        that                ⁢                                  xe2x80x83                                ⁢                remained                ⁢                                  xe2x80x83                                ⁢                on                ⁢                                  xe2x80x83                                ⁢                the                ⁢                                  xe2x80x83                                ⁢                sieve                            )                                                                                      (                              weight                ⁢                                  xe2x80x83                                ⁢                of                ⁢                                  xe2x80x83                                ⁢                the                ⁢                                  xe2x80x83                                ⁢                test                ⁢                                  xe2x80x83                                ⁢                sample                                                                                                        of                ⁢                                  xe2x80x83                                ⁢                the                ⁢                                  xe2x80x83                                ⁢                treated                ⁢                                  xe2x80x83                                ⁢                filler                            )                                            -                                                      (                              weight                ⁢                                  xe2x80x83                                ⁢                of                ⁢                                  xe2x80x83                                ⁢                the                ⁢                                  xe2x80x83                                ⁢                nontreated                                                                                        filler              ⁢                              xe2x80x83                            ⁢              that              ⁢                              xe2x80x83                            ⁢              remained              ⁢                              xe2x80x83                            ⁢              on                                                                                          the                ⁢                                  xe2x80x83                                ⁢                sieve                            )                                                                                      (                              weight                ⁢                                  xe2x80x83                                ⁢                of                ⁢                                  xe2x80x83                                ⁢                the                ⁢                                  xe2x80x83                                ⁢                test                ⁢                                  xe2x80x83                                ⁢                sample                                                                                                        of                ⁢                                  xe2x80x83                                ⁢                the                ⁢                                  xe2x80x83                                ⁢                nontreated                ⁢                                  xe2x80x83                                ⁢                filler                            )                                          
and measured by the use of a sieve according to the standard NF Xll-501 (325 mesh size). (This standard is publicly available at AFNOR, the French organization of standards.)
This method for measuring the retained quantity during dry sieving involves weighing very precisely 100 g of the filler test sample, followed by pouring the sample into the sieve with a size of 325 mesh.
The sieve is then placed on a mechanical sieve marketed by the company RETSCH GmbH as type 3D and driven, for 30 min, in an oscillatory motion corresponding to a graduation from 50 to 100. After 30 min, the dry retained quantity remaining on the sieve is subjected to the moderate action of a brush in accordance with the standard NF T30-024 so as not to destroy the agglomerates present on the surface of the sieve.
The retained quantity is thus determined by the ratio of the weighed amount of the filler remaining on the sieve to the precise weight of the filler poured onto the sieve.
The mineral fillers so treated, according to the invention, are selected from calcium carbonates of natural or synthetic origin, magnesium carbonate, zinc carbonate, mixed salts of magnesium and calcium such as dolomites, limestone, magnesia, barium sulfate, calcium sulfates, magnesium and aluminum hydroxides, silica, wollastonite, clays and other silica-alumina compounds such as kaolins, silico-magnesia compounds such as talc, mica, solid or hollow glass beads, metallic oxides such as zinc oxide, iron oxides, titanium oxide and, more particularly, those selected from natural or precipitated calcium carbonates such as chalk, calcite, marble, dolomites, aluminum hydroxide, magnesium hydroxide, talc, or mixtures thereof.
The mineral fillers according to the invention differ from the prior art by the fact that they preserve their hydrophilicity while at the same time having an uptake of polyol that is decreased by at least 15%, preferably by at least 20%, with respect to the nontreated mineral filler and, more particularly, in that they are obtained by the treatment method according to the invention.
The polyols used include polyether and polyester polyols.
The polyether polyols that can be used in the present invention include, for example, products made from the addition of propylene oxide to a simple polyol such as glycol, glycerol, trimethylolpropane, and sorbitol in the presence or absence of ethylene oxide; polyether polyols with an amino base, obtained by the addition of propylene oxide or ethylene oxide to amines; halogenated polyether polyols; grafted polyether polyols resulting from the copolymerization of styrene and acrylonitrile in a suspension in a polyether; or polytetramethylene glycol.
The polyester polyols that may be used in the present invention include, for example, those resulting from the polycondensation of polyalcohols with polyacids or their anhydrides such as diacids (for example, adipic acid, phthalic acid), or other acids, which react with diols (for example, ethylene glycol, propylene glycol, butylene glycol, or others) triols (for example, glycerol, trimethylolpropane, or others), and tetrols (for example, pentaerythritol or others), alone or in a mixture.
The polyols also include various hydroxylated compounds such as hydroxylated polybutadienes, prepolymers with hydroxy terminals (resulting from the reaction of an excess of polyol with a diisocyanate), or simple polyols such as glycerol or amino alcohols used in a small quantity with the polyether polyols or polyester polyols to increase the degree of crosslinking.
The uptake of polyol, which reflects the power of absorption of the fillers, is by definition the number of milliliters or grams of polyol used per 100 g or 100 mL of filler matter under the measurement conditions of the test determined by a method derived from the ISO 787/5 standard.
The suspensions of mineral fillers in the polyols according to the invention, which can also contain other mineral and/or organic products such as catalysts and/or antioxidants and/or others, are characterized in that (1) the dry-matter concentration of the treated mineral materials is up to 80 wt % of the suspension; (2) the suspensions present no significant decanting, sedimentation, or thickening after storage at rest for 7 days prior to the manufacture of flexible, semirigid, or rigid polyurethane foams, that is, they have an apparent Brookfield viscosity that is stable and less than that of the suspensions of nontreated mineral fillers; and (3) they contain 0.5-3 wt %, based on the weight of the mineral filler, of a treatment agent with the general formula (I), preferably 0.7-1.5 wt %.
The suspensions so filled, which are homogeneous, stable, and have a low viscosity, according to the invention, are capable of use in the manufacture of flexible, semirigid, or rigid polyurethane foams.
In addition, these flexible, semirigid, or rigid polyurethane foams are used for the preparation of molded or nonmolded objects.